In a conventional network, a direct wireless connection exists between a base station (base station, BS for short) and a user equipment (user equipment, UE for short). With the development of communication technologies, a relay technology is introduced. That is to say, one or more relay nodes (relay node, RN for short) are added between the BS and the UE. The RN is responsible for forwarding a radio signal sent by the BS, where the signal is forwarded one or more times, and finally arrives at the UE. For example, one RN may divide a radio link between a BS and a UE into two radio links: a link from the BS to the RN, and a link from the RN to the UE. In this way, a low-quality link can be replaced with two high-quality links to achieve higher link capacity and better coverage.
Taking the LTE technology as an example, BSs may be interconnected through an X2 interface. After the RN is introduced, an S1/X2 interface exists between the RN and its donor base station (Donor BS, DBS for short). Therefore, the DBS will provide an S1/X2 interface proxy (proxy) function between the RN and other network nodes. For example, the DBS provides an S1 interface proxy function between the RN and a mobility management entity (mobility management entity, MME for short), and also provides an S1 interface proxy (proxy) function between the RN and a serving gateway (serving gateway, SGW for short), and provides an X2 interface proxy function between the RN and the BS. In other words, information transferred between the RN and the BS needs to be processed and forwarded by the DBS. After the RN is introduced, the DBS may serve the UE; and the RN controlled by the DBS may also serve as a base station to serve the UE.
In the prior art, when a UE moves, due to randomness of the UE location and diversity of services, a cell may be excessively loaded or even congested while the load of a neighboring cell of the cell may be very light. The signal coverage of the cell intersects the signal coverage of its neighboring cell. For example, if overlapped signal coverage exists between two cells, the two cells are in a neighbor relationship with each other and are neighboring cells of each other. Similarly, if more than one base station serves the neighboring cell, the more than one base station may be called neighboring base stations of each other.
A feasible means of relieving the heavy load of the cell is negotiation between cells, for example, negotiation between a cell and its neighboring cell. For example, an excessively loaded cell requests a lightly-loaded neighboring cell to share the load generated by some UEs, that is, UEs at the edge of the excessively loaded cell are handed over to the lightly-loaded neighboring cell to achieve load balance between cells, maximize network resource utilization, and improve system capacity and system performance.
However, up to now, no effective method is available to solve the issue of mobility load balance between cells after an RN is introduced.